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Fix legend labelcolor=‘linecolor’ to handle various corner cases, e.g. step histograms and transparent markers #30328

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Fix legend labelcolor=‘linecolor’ to handle various corner cases, e.g. step histograms and transparent markers #30328

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dabaf62
add tests for various corner cases of legends with `labelcolor` set t…
lukashergt Jul 18, 2025
335e76e
fix legends with `labelcolor` set to `linecolor`: change ordering fro…
lukashergt Jul 18, 2025
8d9555e
account for the `classic` style in the mpl tests; need to specify `no…
lukashergt Jul 18, 2025
0fc6fbe
remove unnecessary `loc=1` in new tests for `labelcolor_linecolor`
lukashergt Jul 18, 2025
db46a5c
use `mpl.colors.same_color` also for the `none` checks
lukashergt Jul 18, 2025
64e3a86
Apply suggestions from code review
lukashergt Jul 18, 2025
dc425b0
revert to original behaviour of having black legend labels for invisi…
lukashergt Jul 23, 2025
e2122db
compactify tests for `legend_labelcolor_linecolor` as suggested in PR
lukashergt Jul 24, 2025
e6aa6a1
remove unneeded calls to `plt.close`
lukashergt Jul 24, 2025
7d2f76b
use tuple unpacking in `legend_labelcolor_linecolor` tests as suggest…
lukashergt Jul 24, 2025
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20 changes: 15 additions & 5 deletions lib/matplotlib/legend.py
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -576,7 +576,11 @@ def __init__(
# set the text color

color_getters = { # getter function depends on line or patch
'linecolor': ['get_color', 'get_facecolor'],
'linecolor': ['get_markerfacecolor',
'get_facecolor',
'get_markeredgecolor',
'get_edgecolor',
'get_color'],
'markerfacecolor': ['get_markerfacecolor', 'get_facecolor'],
'mfc': ['get_markerfacecolor', 'get_facecolor'],
'markeredgecolor': ['get_markeredgecolor', 'get_edgecolor'],
Expand All @@ -596,18 +600,24 @@ def __init__(
try:
color = getattr(handle, getter_name)()
if isinstance(color, np.ndarray):
if (
color.shape[0] == 1
or np.isclose(color, color[0]).all()
if color.size == 0:
continue
elif (
color.shape[0] == 1
or np.isclose(color, color[0]).all()
):
text.set_color(color[0])
else:
pass
elif cbook._str_lower_equal(color, 'none'):
continue
elif mpl.colors.to_rgba(color)[3] == 0:
continue
else:
text.set_color(color)
break
except AttributeError:
pass
continue
elif cbook._str_equal(labelcolor, 'none'):
for text in self.texts:
text.set_color(labelcolor)
Expand Down
195 changes: 195 additions & 0 deletions lib/matplotlib/tests/test_legend.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1068,6 +1068,201 @@ def test_legend_labelcolor_rcparam_markerfacecolor_short():
assert mpl.colors.same_color(text.get_color(), color)


def assert_last_legend_patch_color(histogram, leg, expected_color,
facecolor=False, edgecolor=False):
"""
Check that histogram color, legend handle color, and legend label color all
match the expected input. Provide facecolor and edgecolor flags to clarify
which feature to match.
"""
label_color = leg.texts[-1].get_color()
patch = leg.get_patches()[-1]
histogram = histogram[-1][0]
assert mpl.colors.same_color(label_color, expected_color)
if facecolor:
assert mpl.colors.same_color(label_color, patch.get_facecolor())
assert mpl.colors.same_color(label_color, histogram.get_facecolor())
if edgecolor:
assert mpl.colors.same_color(label_color, patch.get_edgecolor())
assert mpl.colors.same_color(label_color, histogram.get_edgecolor())


def test_legend_labelcolor_linecolor_histograms():
x = np.arange(10)

# testing c kwarg for bar, step, and stepfilled histograms
fig, ax = plt.subplots()
h = ax.hist(x, histtype='bar', color='r', label="red bar hist with a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)

h = ax.hist(x, histtype='step', color='g', label="green step hist, green label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'g', edgecolor=True)

h = ax.hist(x, histtype='stepfilled', color='b',
label="blue stepfilled hist with a blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'b', facecolor=True)

# testing c, fc, and ec combinations for bar histograms
h = ax.hist(x, histtype='bar', color='r', ec='b',
label="red bar hist with blue edges and a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)

h = ax.hist(x, histtype='bar', fc='r', ec='b',
label="red bar hist with blue edges and a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)

h = ax.hist(x, histtype='bar', fc='none', ec='b',
label="unfilled blue bar hist with a blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)

# testing c, and ec combinations for step histograms
h = ax.hist(x, histtype='step', color='r', ec='b',
label="blue step hist with a blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)

h = ax.hist(x, histtype='step', ec='b',
label="blue step hist with a blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)

# testing c, fc, and ec combinations for stepfilled histograms
h = ax.hist(x, histtype='stepfilled', color='r', ec='b',
label="red stepfilled hist, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)

h = ax.hist(x, histtype='stepfilled', fc='r', ec='b',
label="red stepfilled hist, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)

h = ax.hist(x, histtype='stepfilled', fc='none', ec='b',
label="unfilled blue stepfilled hist, blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'b', edgecolor=True)

h = ax.hist(x, histtype='stepfilled', fc='r', ec='none',
label="edgeless red stepfilled hist with a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_patch_color(h, leg, 'r', facecolor=True)


def assert_last_legend_linemarker_color(line_marker, leg, expected_color, color=False,
facecolor=False, edgecolor=False):
"""
Check that line marker color, legend handle color, and legend label color all
match the expected input. Provide color, facecolor and edgecolor flags to clarify
which feature to match.
"""
label_color = leg.texts[-1].get_color()
leg_marker = leg.get_lines()[-1]
assert mpl.colors.same_color(label_color, expected_color)
if color:
assert mpl.colors.same_color(label_color, leg_marker.get_color())
assert mpl.colors.same_color(label_color, line_marker.get_color())
if facecolor:
assert mpl.colors.same_color(label_color, leg_marker.get_markerfacecolor())
assert mpl.colors.same_color(label_color, line_marker.get_markerfacecolor())
if edgecolor:
assert mpl.colors.same_color(label_color, leg_marker.get_markeredgecolor())
assert mpl.colors.same_color(label_color, line_marker.get_markeredgecolor())


def test_legend_labelcolor_linecolor_plot():
x = np.arange(5)

# testing line plot
fig, ax = plt.subplots()
l, = ax.plot(x, c='r', label="red line with a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'r', color=True)

# testing c, fc, and ec combinations for maker plots
l, = ax.plot(x, 'o', c='r', label="red circles with a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'r', color=True)

l, = ax.plot(x, 'o', c='r', mec='b', label="red circles, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'r', color=True)

l, = ax.plot(x, 'o', mfc='r', mec='b', label="red circles, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'r', facecolor=True)

# 'none' cases
l, = ax.plot(x, 'o', mfc='none', mec='b',
label="blue unfilled circles, blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'b', edgecolor=True)

l, = ax.plot(x, 'o', mfc='r', mec='none', label="red edgeless circles, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'r', facecolor=True)

l, = ax.plot(x, 'o', c='none', mec='none',
label="black label despite invisible circles for dummy entries")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_linemarker_color(l, leg, 'k')


def assert_last_legend_scattermarker_color(scatter_marker, leg, expected_color,
facecolor=False, edgecolor=False):
"""
Check that scatter marker color, legend handle color, and legend label color all
match the expected input. Provide facecolor and edgecolor flags to clarify
which feature to match.
"""
label_color = leg.texts[-1].get_color()
leg_handle = leg.legend_handles[-1]
assert mpl.colors.same_color(label_color, expected_color)
if facecolor:
assert mpl.colors.same_color(label_color, leg_handle.get_facecolor())
assert mpl.colors.same_color(label_color, scatter_marker.get_facecolor())
if edgecolor:
assert mpl.colors.same_color(label_color, leg_handle.get_edgecolor())
assert mpl.colors.same_color(label_color, scatter_marker.get_edgecolor())


def test_legend_labelcolor_linecolor_scatter():
x = np.arange(5)

# testing c, fc, and ec combinations for scatter plots
fig, ax = plt.subplots()
s = ax.scatter(x, x, c='r', label="red circles with a red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)

s = ax.scatter(x, x, c='r', ec='b', label="red circles, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)

s = ax.scatter(x, x, fc='r', ec='b', label="red circles, blue edges, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)

# 'none' cases
s = ax.scatter(x, x, fc='none', ec='b', label="blue unfilled circles, blue label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'b', edgecolor=True)

s = ax.scatter(x, x, fc='r', ec='none', label="red edgeless circles, red label")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'r', facecolor=True)

s = ax.scatter(x, x, c='none', ec='none',
label="black label despite invisible circles for dummy entries")
leg = ax.legend(labelcolor='linecolor')
assert_last_legend_scattermarker_color(s, leg, 'k')


@pytest.mark.filterwarnings("ignore:No artists with labels found to put in legend")
def test_get_set_draggable():
legend = plt.legend()
Expand Down
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